For years, Sam Beam, also known as Iron & Wine, would feel a little twinge of excitement when he opened his mailbox. Every few months or so, he’d find an envelope with a cassette tape inside, one that would often introduce him to songs he’d never heard of before, but which he’d inevitably end up falling in love with.

The tapes were from his friend, Ben Bridwell, whom he grew up with outside Columbia, S.C., and who was living in Seattle. Beam would then fill his own blank tape up with songs he loved and send it back to his friend from his house in Florida.

“We would send each other stuff just to keep up, either music that we had happened upon, new music or old music that we thought each other would like, or stuff that we were working on,” Beam said. “We just sort of kept up with each other that way.”

And then, life got busy — Beam and Bridwell found success with music projects, Beam with Iron & Wine and Bridwell with the group Band of Horses, got married and had kids.

But they never lost their love for discovering and sharing new music. They’ve turned that love into a joint album, “Sing Into My Mouth,” which features covers of songs by acts as varied as Bonnie Raitt, the Talking Heads, Sade and Marshall Tucker Band. They’re currently touring behind the album, with a stop Monday in Atlanta at the Tabernacle.

“We just picked up where we left off,” Beam said. “It was fun this time. We were able to reinterpret the music that we were exchanging instead of just listening.”

Assembling the album was a natural process — they both offered up songs they thought might be fun to reinterpret, some of which had some meaning to them, and some they just thought sounded cool. The Sade song “Bulletproof Soul” was a nod to Bridwell’s father, who is a big fan of the smooth jazz singer. Beam suggested the Them Two song “Am I A Good Man?,” thinking he had unearthed a hidden gem that would be an impressive contribution — it turned out that Bridwell had been performing the song with his band for the past couple of years.

Recording the songs was just as organic of a process, with Beam’s band with the pair in the studio, and everyone collaborating on how the songs should be reinterpreted. Several of the members of the band are composers in their own right, so experimentation was welcome.

“It was done in the spirit of friends making a record,” Beam said. “There was no expectation of what this record should be, so we didn’t have any kind of strong art aesthetic argument to make. We were just going in and seeing what happened. Lots of times, we’d start playing the recorded version, and people would just start falling in with ideas.”

Even after the final tracklist for the album was whittled down, Beam and Bridwell were left with several tracks they still wanted to record. So does that mean there might be a sequel to “Sing Into My Mouth”?

“Yeah, maybe,” Beam said. “Never say never. We had a ball making it, so I would love to do it again.”